Known by the terms tooth implant or dental implant, a wide variety of denture systems have been available on the market for years and have in some cases been used with great success. The terms tooth implant or dental implant generally denote the denture per se and should not be confused with the actual implant body which, as a replacement for a tooth root, is correctly designated as the implant. In the text below, the terms tooth implant and implant body or implant are clearly distinguished, where the tooth implant designates the denture, which comprises the implant body for anchoring in the jawbone. Two-part and three-part tooth implants are mainly available on the market, of which the three-part implants for replacement of an individual tooth generally consist of an endosteal implant or implant body, an abutment (also called a connection part or implant post), and a crown, a bridge or another prosthetic.
The abutment allows the dentist to orient the crown with respect to the implant, such that the exact position of the crown in the dental arch is not dependent only on the position of the implant body. For this purpose, the abutment has to be positioned in the implant according to a predefined orientation, after the implant has been anchored in the jaw.
Customary implant forms include blade, needle, screw, cylinder and cone implants, which are each used for different indications. In principle, subperiosteal and endosteal implants can be used. Commonly used endosteal implants are substantially cylindrical and are screwed or hammered into a drilled hole in the jawbone or directly into the jawbone. At the coronal end, the implants are provided with an open blind bore for receiving the abutment. In the last few decades, the material mainly used has been titanium, since it has a modulus of elasticity similar to the jawbone and has excellent biocompatibility. Alternatively, ceramics can be used, e.g. zirconia ceramic. In such tooth implants, the crown, mostly made of conventional dental ceramic and/or metal, is adhesively bonded or cemented onto the abutment or the one-part implant/abutment construction or secured thereon by mechanical means.
EP 0 879 024 B1 discloses a system in which a solid conical abutment is screwed into an implant. A receiving opening of the implant is likewise correspondingly formed with a conical shape. A conical shape of this kind is favored by dentists since it simplifies the implantation, in particular also the taking of impressions and the production of master models. The conical implant-abutment connection places high demands on the precision fit of the components, since it is both a form-fit and also a force-fit connection. Since the dental implants have to take up considerable alternating loads during chewing, even the very slightest mobility between the screwed components leads to abrasion and wear. Moreover, the screwing-together of abutment and implant is a complicated procedure in which the threads first of all have to engage in each other and then the abutment, generally by being rotated several times, is introduced axially into the implant.
WO 2006/084346 A1 discloses an implant system with an abutment made of a non-metallic material, which system comprises an implant and a prosthesis support, which in turn comprises an abutment and a collar element. Essential features of the implant system are that the parts of the implant system are pushed linearly into one another and adhesively bonded to one another. Between a substantially cylindrical base post and a head part, the abutment has a cylindrical neck part with a lower projection, which is designed as a polygon and serves for the radial positioning of the abutment in a corresponding recess in the shoulder of the implant. The central bore in the implant for receiving the base post is provided with an inner thread, which allows a screw cap or a spacer to be screwed in during the process of incorporation. After the incorporation, a collar element is pushed over the neck area of the abutment, and the base post is adhesively bonded into the threaded bore of the implant. A central and continuous axial channel is provided in the abutment to allow the adhesive to flow off A disadvantage of this system lies in the considerable technical effort in producing the central axial channel in the abutment and in the mechanical loads and stresses to which the abutment is exposed.
EP 1 728 486 A1 discloses an implant system with an implant and an abutment, in which the abutment is provided with means for blocking the abutment in rotation in the implant. A receiving opening in the implant is designed in such a way that a base portion of the abutment can be inserted substantially with a form fit into the receiving opening at the desired angle position and is secured in this position by a separate screw on the implant.
In the known systems in which an abutment is pushed into an implant, the abutment has to be held in position by application of a force while, for example, an integral bond is formed by the adhesive material. As a result of the pressing force, adhesive is distributed along the superposed surfaces, can partially swell out of the interstices and, during hardening, can change the position between abutment and implant, e.g. by lifting the abutment in the implant (pump effect). This causes difficulties, particularly in the case of bone-level implants. When inserting the abutment, the person providing the treatment is often under pressure of time, since the adhesive material often hardens quickly. The person providing the treatment scarcely has time to check the correct position of the abutment relative to the implant, and there is a risk of incorrect positioning. For a patient, the time waiting for the abutment to be secured is unpleasant, since constant pressure applied to the jawbone has to be withstood.